The present invention relates to a method for depositing a fluorine containing carbon film, which can be used as, e.g., an interlayer dielectric film (an interlayer dielectric film) of a semiconductor device, by a plasma treatment.
In order to achieve the high integration of a semiconductor device, it has been developed to provide devices, such as the scale down of a pattern and the multilayering of a circuit. As one of such devices, there is a technique for multilayering wirings. In order to provide a multi-layer metallization structure, a number n wiring layer and a number (n+1) wiring layer are connected to each other by means of a conductive layer, and a thin-film called an interlayer dielectric film as an interlayer dielectric film is formed in a region other than the conductive layer.
A typical interlayer dielectric film is an SiO2 film. In recent years, in order to more accelerate the operation of a device, it has been required to reduce the relative dielectric constant of the interlayer dielectric film, and the material of the interlayer dielectric film has been studied. That is, the relative dielectric constant of an SiO2 film is about 4, and it has been diligently studied to dig up materials having a smaller relative dielectric constant than that of the SiO2 film. As one of such materials, it has been studied to put an SiOF film having a relative dielectric constant of 3.5 to practical use. The inventor has taken notice of a fluorine containing carbon film (which will be hereinafter referred to as a xe2x80x9cCF filmxe2x80x9d) having a still smaller relative dielectric constant.
FIG. 19 shows a part of a circuit part formed on a wafer, wherein reference numbers 11 and 12 denote CF films, 13 and 14 denoting conductive layers of tungsten (w), 15 denoting a conductive layer of aluminum (Al), 16 denoting an SiO2 film, into which P and B have been doped, and 17 denoting an n-type semiconductor region. The W layer 13 is formed at a process temperature of 400 to 450xc2x0 C. At this time, the CF films 11 and 12 are heated to the process temperature. However, if the CF films are heated to such a high temperature, a part of Cxe2x80x94F bonds are cut, so that F (fluorine) gases are mainly desorbed. The F gasses include F, CF, CF2 gases and so forth.
If the F gases are thus desorbed, there are the following problems.
(a) The metal wirings of aluminum, tungsten and so forth are corroded.
(b) Although the insulator film also has the function of pressing the aluminum wiring to prevent the swell of aluminum, the pressing force of the insulator film on the aluminum wiring is decreased by the degassing. As a result, the aluminum wiring swells, so that an electrical defect called electromigration is easily caused.
(c) The insulator film cracks, so that the insulation performance between the wirings gets worse. When the extent of the crack increases, it is not possible to form any wiring layers at the next stage.
(d) If the amount of desorbed F increases, the relative dielectric constant increases.
It is therefore an object of the present invention to eliminate the aforementioned problems and to provide a method capable of depositing an insulator film of a CF film, which has strong bonds and which is difficult to be decomposed, e.g., an interlayer dielectric film of a semiconductor device.
According to one aspect of the present invention, according to a first aspect of the present invention, a plasma thin-film deposition method comprises the steps of: activating a thin-film deposition gas containing cyclic C5F8 gas to form a plasma; and depositing an insulator film of a fluorine containing carbon film on a substrate to be treated, with the plasma.
The thin-film deposition gas may contain cyclic C5F8 gas and at lease one of a hydrocarbon gas and hydrogen. The insulator film may be deposited under a process pressure of 5.5 Pa or lower. The temperature of the substrate to be treated may be 360xc2x0 C. or higher.
According to a second aspect of the present invention, a plasma thin-film deposition method comprises the steps of: activating a thin-film deposition gas containing linear C5F8 gas to form a plasma; and depositing an insulator film of a fluorine containing carbon film on a substrate to be treated, with the plasma.
The thin-film deposition gas may contain linear C5F8 gas and at lease one of a hydrocarbon gas and hydrogen. The insulator film may be deposited under a process pressure of 0.3 Pa or lower. The temperature of the substrate to be treated may be 360xc2x0 C. or higher.
According to a third aspect of the present invention, a plasma thin-film deposition method comprises the steps of: activating a thin-film deposition gas containing a gas of a benzene ring containing compound to form a plasma; and depositing an insulator film of a fluorine containing carbon film on a substrate to be treated, with the plasma.
The benzene ring containing compound may be a compound of C and F. The compound of C and F may be C6F6. The compound of C and F may also be C7F8. Alternatively, the benzene ring containing compound may be a compound of C, F and H. The compound of C, F and H may be C7H5F3.
According to the first through third aspects of the present invention, it is possible to produce a CF film which has high thermostability and a small amount of desorbed F gas. Therefore, if this CF film is used as, e.g., an interlayer dielectric film of a semiconductor device, it is possible to prevent the corrosion of a metal wiring, the swell of an aluminum wiring and the crack of the film. Since CF films have been widely noticed as insulator films having a small relative dielectric constant and since the scale down and high integration of semiconductor devices have been required, the present invention is effective in the practical use of CF films as insulator films.